Dear Lifehacker, I'm upgrading my phone and selling my old one on eBay. How do I make sure all my personal data is off of the phone before I sell it off to someone else? Sincerely, Particular About Privacy
It's surprising how many people sell their phones without doing anything to remove private data. Selling your phone to a stranger as-is gives that stranger access all your music, email, text messages and other data for a few hundred dollars. To make sure your private data's safe, you'll want to do a full wipe of your phone before you sell it off. This is actually very easy to do, on both the iPhone or Android. Here's how:
How to Wipe an iPhone
Wiping the iPhone is incredibly simple. Just head into the Settings app on your phone, go to the General section, and scroll all the way down to the bottom of the menu. You should see a button that says "Reset". Tap that and hit the "Erase All Content and Settings" button. This will do a full wipe of all your media, settings and other data, so your phone is just like it was out of the box for your new buyer.
For what it's worth, you can also plug it into iTunes and hit the "Restore" button. This is nice if you want to make one last backup before you wipe, since you'll have to be in iTunes anyway. Either method should work fine. Note that both methods will also un-jailbreak your phone, if it was jailbroken.
How to Wipe an Android Phone
Android phones are easy to wipe, but require a few more button taps. Unlike the iPhone, your Android phone has multiple hard drives inside it. It has its internal memory, where most of your apps and system settings are stored, and your SD card, where your music, pictures, and some app settings are stored. Some phones, like the Droid Incredible, even have two SD cards. So, when wiping, you want to make sure you get everything.
If your SD card came with your phone, I'd recommend wiping it and selling it with the phone. If you bought your SD card separately, though, you might as well keep it for yourself and use it on your next phone (unless you want to sell it with your phone and bring up the price a bit). If you're keeping it, you don't need to wipe it. However, if your phone did come with an SD card, whether it's the one you're using right now or not, it's a good idea to pop it in, wipe it, and sell it with the phone.
To wipe your phone, head into Settings > SD & Phone Storage. First, hit the "Unmount SD Card" option. When it finishes unmounting the card, you'll see the "Format SD Card" button will no longer be greyed out. Click on that to wipe your SD card. When that's done, hit the "Factory Data Reset" button. This will erase all your other data, and return your phone to what it was like when you bought it. If you have a Droid Incredible or other two-SD-card phone, you should have a third option to wipe that internal storage, which you'll also want to do.
Note that if you have a rooted phone, this process will not remove root, and it won't remove any custom ROMs you're running. To do that, you'll need to use a program like Motorola's RSD Lite (if you have a Motorola phone) to fully wipe your phone. You may need a different program depending on your manufacturer. That said, you could also sell your phone as rooted — some people prefer to buy their phone pre-rooted, and there are online sellers that support selling rooted and ROMed phones.
That's it! It's very simple to prepare your phone for sale, and you don't need to do that much to keep your data safe. Enjoy your new phone!